4-211. HEIGHT SENSING BRAKE PROPORTIONING VALVE REPLACEMENT.
This task covers:
General Safety Instructions
Transmission in (N) neutral
General Mechanics Tool Kit
Parking brake and micro-brakelock set.
Proportioning Valve Adjustment Gauge
Brake Fluid (Appendix D, Item 4)
Adding any type of suspension
accessories or making modification
that will change the distance
between the axle and the frame
without changing the load, will
provide a false reading to the
brake proportioning valve which
could provide unsatisfactory brake
performance, resulting in an
accident and possible injury.
a. Raise the vehicle and support the frame with
suitable safety stands, allowing the axle to hang
b. Clean the exterior of the valve connections to
optimum brake balance and
prevent dirt and other foreign materials from
The vehicle braking
contaminating the hydraulic system.
force is distributed to the front and
rear wheels as determined by
c. Disconnect the brake pipes (1), plugging them
either a light or heavy payload
to prevent loss of fluid or entrance of dirt.
condition. The valve is mounted
d. Remove the nut (2) from the shaft and
on the frame and a linkage
disconnect the lever (3).
connects the valve to a bracket
that is mounted on the axle.
e. Disconnect the bolts (4) and washers (5) and
remove the valve (6).